The γ-circular polarizations (${\mathit{P}}_{\gamma }$) and asymmetries (${\mathit{A}}_{\gamma }$) of the parity forbidden M1+E2 γ decays, ${}_{}{}^{36}{}_{}{}^{}\mathrm{Cl}_{}^{\mathrm{*}}{}_{}{}^{}$(${\mathit{J}}^{\mathrm{\pi }}$=$2^{\mathrm{-}}$;T=1;${\mathit{E}}_{\mathit{x}}$=1.95 MeV)${\to }^{36}$Cl(${\mathit{J}}^{\mathrm{\pi }}$=$2^{+}$;T=1; g.s.) and ${}_{}{}^{36}{}_{}{}^{}\mathrm{Ar}_{}^{\mathrm{*}}{}_{}{}^{}$(${\mathit{J}}^{\mathrm{\pi }}$=$2^{\mathrm{-}}$;T=0;${\mathit{E}}_{\mathit{x}}$=4.97 MeV) ${\to }^{36}$${\mathrm{Ar}}^{\mathrm{*}}$(${\mathit{J}}^{\mathrm{\pi }}$-$2^{+}$;T=0;${\mathit{E}}_{\mathit{x}}$=1.97 MeV), are investigated theoretically. We use the recently proposed Warburton-Becker-Brown shell-model interaction. For the weak forces we discuss comparatively different weak interaction models based on different assumptions for evaluationg the weak meson-hadron coupling constants. The results determine a range of ${\mathit{P}}_{\gamma }$ values from which we find the most probable values: ${\mathit{P}}_{\gamma }$=1.1×${10}^{\mathrm{-}4}$ for ${}_{}{}^{36}{}_{}{}^{}\mathrm{Cl}$ and ${\mathit{P}}_{\gamma }$=3.5×${10}^{\mathrm{-}4}$ for ${}_{}{}^{36}{}_{}{}^{}\mathrm{Ar}$.

Using a primary beam of ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$ at 650 MeV/nucleon impinging on a beryllium target, production cross sections of proton-rich fragments from projectile fragmentation have been measured at the projectile-fragment separator FRS at Gesellschaft für Schwerionenforschung Darmstadt m.b.H. The experimental data ranging from nickel to scandium for isotopes close to stability as well as for fragments at the proton drip line are compared to predictions of the microscopic ISApace code, to calculations with a revised abrasion-ablation model and with the statistical abrasion model, and to the results of the empirical parametrization EPAX. Besides these systematic measurements, evidence for the particle stability of ${}_{}{}^{50}{}_{}{}^{}\mathrm{Ni}$ has been found for the first time, whereas the nuclei ${}_{}{}^{49}{}_{}{}^{}\mathrm{Co}$ and ${}_{}{}^{54}{}_{}{}^{}\mathrm{Cu}$ are shown to be unbound. These observations are compared to mass predictions.

Excitation functions were measured by the stacked-foil technique for ${}_{}{}^{\mathrm{nat}}{}_{}{}^{}\mathrm{Fe}$(p,xn${)}^{56}$Co, ${}_{}{}^{\mathrm{nat}}{}_{}{}^{}\mathrm{Fe}$(p,xn${)}^{57}$Co, ${}_{}{}^{58}{}_{}{}^{}\mathrm{Fe}$(p,n${)}^{58}$${\mathrm{Co}}^{\mathit{m}+\mathit{g}}$, ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$(p,α${)}^{54}$Mn, ${}_{}{}^{\mathrm{nat}}{}_{}{}^{}\mathrm{Fe}$(d,xn${)}^{58}$${\mathrm{Co}}^{\mathit{m}+\mathit{g}}$, ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$(d,2n${)}^{56}$Co, ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$(d,α${)}^{54}$Mn, ${}_{}{}^{55}{}_{}{}^{}\mathrm{Mn}$(α,n${)}^{58}$${\mathrm{Co}}^{\mathit{m}+\mathit{g}}$, and ${}_{}{}^{55}{}_{}{}^{}\mathrm{Mn}$(α,2n${)}^{57}$Co reactions from the respective thresholds to 14.12 MeV in work with protons, 12.97 MeV with deuterons, and 25.52 MeV with alpha particles. The radioactivity of the activation products was determined by high resolution γ-ray spectroscopy. Statistical model calculations taking into account the precompound effects were performed for all the reactions, using a consistent set of model parameters. The experimental excitation functions of the proton and alpha-particle induced reactions are described within 10 to 15 percent by the calculation over the whole investigated energy range. The shapes of the excitation functions of the deuteron induced reactions are also reproduced well by the model calculation. However, a reduction factor (R=0.56) is needed to take account of the direct breakup process and, thereby, to obtain good agreement between the experimental data and model calculations.

The isotropic distributions of projectile fragmentation have been measured for the reactions of 44 MeV/nucleon ${}_{}{}^{129}{}_{}{}^{}\mathrm{Xe}$ on ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$ and ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$ targets. The systematics of the production cross sections are discussed via some macroscopic models.

Fragment-fragment correlations are used to probe the spatial-temporal extent of the emitting source in central ${}_{}{}^{36}{}_{}{}^{}\mathrm{Ar}$${+}^{197}$Au reactions at E/A=35, 50, 80, and 110 MeV. The experimental two particle correlations are compared both with the Koonin-Pratt two-body formalism as well as a three-body Coulomb trajectory calculation. The spatial-temporal extent of the emitting system decreases with increasing incident energy. Within the context of a three-body Coulomb trajectory model the mean fragment emission time rises sharply as a function of the assumed density of the system until ρ/${\mathrm{\rho }}_0$≊0.3. If one assumes a fixed density, the extracted mean emission time decreases with increasing assumed charge of the emitting system. Assuming ρ/${\mathrm{\rho }}_0$≊0.3 the mean emission time τ according to calculations using a three-body Coulomb trajectory model, is ≊115–135 fm/c at E/A=50 MeV and ≊75–100 fm/c at E/A=110 MeV. Comparisons with a generalized N-body Coulomb trajectory model demonstrate that the effect of interactions with other emitted particles is negligible. The prediction of a microcanonical model which includes pre-emission correlations between the fragments is compared to the measured correlation function at E/A=110 MeV.

Double differential cross sections for (p,n) quasifree scattering on p-shell nuclei, ${}_{}{}^{6,7}{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^{10,11}{}_{}{}^{}\mathrm{B}$, and ${}_{}{}^{12,13}{}_{}{}^{}\mathrm{C}$, have been measured at an incident proton energy of 186 MeV between ${\mathrm{\theta }}_{\mathrm{lab}}$=θ° and ${\mathrm{\theta }}_{\mathrm{lab}}$=50° in steps of 5°. The normal polarization transfer coefficient, analyzing power, and induced polarization were also measured at ${\mathrm{\theta }}_{\mathrm{lab}}$=0°, 15°, and 20° using an incident proton beam of transverse polarization. Calculations by some competing quasifree models are presented and compared with the experimental results.

Energy-sharing distributions have been measured at five quasifree angle pairs for the reaction ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$(α,2α${)}^5$He at an incident energy of 197 MeV. In order to extract absolute spectroscopic factors, elastic scattering cross sections for ${}_{}{}^4{}_{}{}^{}\mathrm{He}$(α,α${)}^4$He were also measured at approximately the same incident energy, between center-of-mass angles of 40° and 90°. The knockout data are compared with distorted-wave impulse approximation theory. The extracted cluster spectrosopic factors are found to be in agreement with a theoretical estimate and also with existing results from (p,pα) studies. Consequently, this new result is in strong contrast to those from previous (α,2α) studies at lower incident energies which yield spectroscopic factors significantly in excess of the expected values. The radial localization of the coincidence cross section in the target nucleus suggests that the observed incident energy dependence of the spectroscopic factors is related to the cluster-core nuclear density. Thus the cluster formation probability is enhanced in the region of very low nuclear density which is preferentially sampled by the (α,2α) reaction at low incident energies.

The problem of heavy-ion fusion reactions in the one-dimensional barrier penetration model (BPM) has been reexamined in light of supersymmetry-inspired WKB (SWKB) method. Motivated by our recent work [Phys. Lett. A 184, 209 (1994)] describing the SWKB method for the computation of the transmission coefficient T(E), we have performed similar calculations for a potential barrier that mimics the proximity potential obtained by fitting experimentally measured fusion cross section ${\mathrm{\sigma }}_{\mathit{F}}$(E) for the light-light and light-heavy systems. For illustration, we have first dealt with an analytically solvable potential which interpolates between two well-known nuclear barriers such as the Morse and the Eckart for two limiting values of the free parameter of the potential. Comparison of the predicted T(E) with the exact analytic ones reveals that the present scheme yields consistently better results than those obtained from the WKB approximation. Furthermore, in contrast to the WKB method, analytic continuation of our SWKB transmission coefficient for the corresponding potential well (obtained through the inversion procedure) leads to exact energy eigenvalues. We have further studied the energy dependence of the total fusion cross section for different processes such as ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$${+}^{12}$C${,}^{19}$F+ ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$${,}^{16}$O${+}^{208}$Pb, and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ with even isotopes of Sm, using a parametrized potential barrier suggested by Ahmed. The predicted cross sections are in agreement with values obtained from the WKB method and with direct experimental measurements for the beam energy near and above the Coulomb barrier. In the case of sub-barrier fusion, our results are substantially better than those given by the Hill-Wheeler parabolic approximation which overestimates ${\mathrm{\sigma }}_{\mathit{F}}$(E), especially for the light-ion systems.

The probability of excitation of atomic electrons during various nuclear reactions has been calculated. Appropriate corrections to some experimentally determined threshold and resonance energies are given.

A method for calculating multistep direct reactions for both continuum and discrete levels is proposed. The energy-angle correlation scattering kernel is adopted for continuum and discrete levels in the semiclassical approach, in which the angular momentum and parity conservations are considered. Then, following the Feshbach, Kerman, and Koonin quantum multistep direct reactions theory, the Legendre coefficients of the angular distributions are calculated based on one-step distorted-wave Born approximation instead of nucleon-nucleon scattering expressions in nuclear matter. Since the quantum effects are properly considered, we call it the quasiquantum multistep direct reactions theory. For the specific reaction considered here, the calculated discrete level neutron angular distributions of the ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$(p,${\mathit{n}}_0$${)}^{11}$C reaction and the cross sections of the ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$(p,${\mathit{n}}_0$${)}^{11}$C and the ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$(p,n${)}^{11}$C reactions reproduce the experimental data reasonably. This approach can also be used to composite particle emissions.

We investigate the role of the full dynamical dependence of the free off-shell nucleon-nucleon t matrix on the optical potential for proton-nucleus elastic scattering in the 100–400 MeV incident energy range within a full-folding model context. Particular emphasis is placed on the effects of deuteron formation by explicitly taking into account pole singularities in the free nucleon-nucleon t matrix. The full-folding model for the optical potential provides a flexible framework for this purpose as it allows the sampling of the internucleon effective force both off shell and as a function of the energy available in the center of mass for the interacting nucleon pair. A comparison of calculated and measured scattering observables for proton elastic scattering on ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ leads to the conclusion that the full off-shell free t matrix is a poor approximation for that part of the nucleon-nucleon effective force required for calculating optical potentials below ∼250 MeV. Medium effects and higher order corrections to the optical potential are necessary to improve our understanding of nucleon scattering.

We show how momentum conservation is fundamental to the description of angular distributions in preequilibrium nuclear reactions. By using state densities with linear momentum to describe the phase space during the preequilibrium cascade, angular distributions can be derived in a transparent way. Fermi-motion and Pauli-blocking effects are included, and correlations between the emission particle’s energy and angle are obtained for all orders of scattering. Our model provides a physical basis for many features of widely used phenomenological systematics of Kalbach, and provides a framework for understanding the systematical properties of continuum angular distributions.

Half-lives and anisotropies in the α decay of ${}_{}{}^{205,207,209}{}_{}{}^{}\mathrm{Rn}$, ${}_{}{}^{219}{}_{}{}^{}\mathrm{Rn}$, ${}_{}{}^{221}{}_{}{}^{}\mathrm{Fr}$, ${}_{}{}^{227,229}{}_{}{}^{}\mathrm{Pa}$, and ${}_{}{}^{229}{}_{}{}^{}\mathrm{U}$ have been calculated using the reaction-theoretical formalism proposed by Jackson and Rhoades-Brown and adapted for axially symmetric deformed nuclei by Berggren and Olanders. The possibility of octupole deformation has been taken into account. In addition, a variant of triaxial octupole deformation has been considered tentatively in the case of ${}_{}{}^{227}{}_{}{}^{}\mathrm{Pa}$ and ${}_{}{}^{229}{}_{}{}^{}\mathrm{Pa}$.

We compute the multifractal moments ${\mathit{G}}_{\mathit{q}}$ in terms of a new scaled variable X suggested by Bialas and Gazdzicki to study the dynamical fluctuations of particles produced in the interactions of ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$ at 10.6A GeV with nuclear emulsion. An asymptotic power-law dependence of the moments on the bin size δX has been observed in pseudorapidity (η), azimuthal (φ), and η-φ phase spaces. The dynamical values of the generalized dimensions are determined in all the phase spaces. The dynamical properties of the produced particles are mapped onto smooth multifractal spectra f(Δ${\mathrm{\alpha }}_{\mathit{q}}$) by excluding the statistical contribution. The ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$ results are compared with a ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ ion at 14.5A GeV and a ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ beam at 200A GeV.

The problem of hadronic cluster production in heavy-ion collisions is studied in search for an observable signature of first-order quark-hadron phase transition. The study is carried out by cellular automata in a two-dimensional model of the mixed phase at midrapidity. The clusters are allowed to grow as well as to coalesce upon collision. The distribution of cluster sizes is found to exhibit scaling behavior that is independent of the size of the mixed region, nucleation radius, and nucleation probability. The universal scaling index γ=1.86±0.18 may be used to characterize and identify the phase transition process. Possible connection with self-organized criticality is pointed out.

The goal of the present study is to see to what extent a ‘‘pure’’ multiple scattering model can describe recent boson interferometry measurements which have been carried out at the CERN SPS. Assuming an initially spherical spacial distribution of the produced particles and with multiplicities, ${\mathit{p}}_{\mathit{T}}$ distributions, and rapidity-distributions taken from experiment, the position and momentum of each particle are allowed to evolve in time while undergoing multiple scatterings with the other particles in the system until freezeout for that particle occurs. Pions, kaons, and nucleons are included in the calculations but no resonance production of hadrons is included. From the resulting space-time and momentum information for each boson, bosons are symmetrized in pairs, a two-boson correlation function is formed, and a Gaussian source parametrization is fitted to extract the radius parameter for the source. It is found that although the present model radius parameters tend to be systematically slightly smaller than the experimental ones in some cases, the ‘‘pure’’ multiple scattering calculation describes well the experimental rapidity, ${\mathit{p}}_{\mathit{T}}$, and boson-type dependences observed at CERN energies.

We estimate freezeout conditions for s, c, and b quarks in high energy nuclear collisions. Freezeout is due either to loss of thermal contact, or to particles ‘‘wandering’’ out of the region of hot matter. We then develop a thermal recombination model in which both single-particle (quark and antiquark) and two-particle (quark-antiquark) densities are conserved. Conservation of two-particle densities is necessary because quarks and antiquarks are always produced in coincidence, so that the local two-particle density can be much larger than the product of the single-particle densities. We use the freezeout conditions and recombination model to discuss heavy resonance production at zero baryon density in high energy nuclear collisions.

We calculate all spin-transfer observables for the quasielastic (p→,n→) reaction in a relativistic plane-wave impulse approximation. The nuclear structure information is contained in a large set of nuclear response functions that are computed in nuclear matter using a relativistic random-phase approximation to the Walecka model. A reduced value of the nucleon mass in the medium induces important dynamical changes in the residual isovector interaction relative to its nonrelativistic counterpart. As a result, good agreement is found for all spin observables—including the spin-longitudinal to spin-transverse ratio—when compared to the original (q=1.72 ${\mathrm{fm}}^{\mathrm{-}1}$) NTOF (neutron time-of-flight facility) experiment. In contrast, the spin-longitudinal to spin-transverse ratio is underpredicted at q=1.2 ${\mathrm{fm}}^{\mathrm{-}1}$ and overpredicted at q=2.5 ${\mathrm{fm}}^{\mathrm{-}1}$. We comment on the role of distortions as a possible solution to this discrepancy.

We construct a model for the pion (valence) structure function that fits the experimental data obtained in the study of the Drell-Yan process. The model may also be used to calculate the structure function of off-mass-shell pions. We apply our model in the study of deep-inelastic scattering from off-mass-shell pions found in the nucleon and are thus able to resolve a problem encountered in the standard analysis of such processes. The usual analysis is made using the structure function of on-mass-shell pions and requires the use of a soft πNN form factor that is inconsistent with standard nuclear physics phenomenology. The use of our off-mass-shell structure functions allows for a fit to the data for nonperturbative aspects of the nucleon ‘‘sea’’ with a pion-nucleon form factor of the standard form.

In this paper a relativistic constituent-quark model based on the Ruijgrok–de Groot formalism is presented. The quark model is not defined in configuration space, but in momentum space. The complete meson spectrum, with the exception of the self-conjugate light unflavored mesons, is calculated. The potential used consists of a one-gluon exchange (OGE) part and a confining part. For the confining part a relativistic generalization of the linear plus constant potential was used, which is well defined in momentum space without introducing any singularities. For the OGE part several potentials were investigated. Retardations were included at all places. By the use of a fitting procedure involving 52 well-established mesons, but results were obtained for a potential consisting of a purely vector Richardson potential and a purely scalar confining potential. Reasonable results were also obtained for a modified Richardson potential. Most meson masses, with the exception of the π, the K, and the ${\mathit{K}}_0^{\mathrm{*}}$, were found to be quite well described by the model.